1. Area of the Art
The present invention relates to membrane electrode devices for electrodeposition coating. In particular the present invention relates to membrane electrode devices for electrodeposition coating (applying an "e-coat"), with an emphasis on the tubular membrane geometry of electrode devices for electrodeposition coating.
2. Description of the Art
Electrodeposition coating generally consists of two basic formats. These include anodic and cathodic systems for electrodeposition coating. Anodic systems refer to the object (+charge) that is being coated. In an embodiment of the system of the present invention, the coating material that is used is of the anodic type, although the present invention is equally applicable to use of the cathodic type.
The Anion type is one in which carboxyl elements cling to resin, aiding in water solubility. To increase the ionization factors of the water soluble coating, an alkaline neutralizing agent such as triethylamine is mixed into the coating solution. During the deposition of the resin molecules through ionization, the concentration of neutralizing agent increases. The coating material is successively replaced from an outside source.
As a by-product of the deposition, there is an accumulation of amine as a neutralizing agent. A phenomenon known as pin holes in the coating is produced if the excessive neutralizing agent is not moved to a specified level. The efficiency of the electrodeposition coating is impaired to a substantial extent by this drawback.
Cathodic systems refer to the object (-charge) that is being coated. In this system the coating material that is used is of Cathodic type. The Cathodic type is one in which amino elements attach to the resin molecules to aid in water solubility. To increase the ionization factors of the water soluble coating, an acidic neutralizing agent such as acetic acid is added. During the deposition of the resin molecules through ionization, the concentration of neutralizing agent increases.
The coating material should be successively replaced from an outside source. As a by-product of the deposition, there is an accumulation of Acetic acid. The phenomenon known as pin holes in the coating is produced if the excessive neutralizing agent is not removed to specified levels. The efficiency of the electrodeposition coating is impaired to a substantial extent by this drawback.
To eliminate and control this aforementioned issue, a pH control is performed for increasing the efficiency. This is accomplished using an electrode and aqueous solution separated and contained by use of an ion-exchange membrane or the like, distanced from the component that is being coated. The ion-exchange membrane allows the migration through osmosis of the amine and acetic acid, thereby preventing the neutralizing agent to concentrate in the aqueous solution. The acetic acid or amine is then mixed with a water solution that flows through the internal area and out the top of the ion-exchange portion of the electrodeposition device.
On the other hand, the use of dry ion-exchange membrane during the manufacturing of these electrodeposition devices causes the membrane to swell an average of 10% upon placement into the aforementioned aqueous solution. This effect combined with the pressure differentials that are present in the environment and mechanics of agitation of the aqueous coating material, forces the membrane to migrate around the devices tubular support structure, thereby reducing the efficiency of the device.
Furthermore, a reaction occurs such that impurities permeated through the ion-exchange membrane and impurities in the water found in the electrode and polarization occurs. Further oxygen molecules are displaced through electrolysis and can not easily be removed through conventional trickle down methods, or simple bottom feed systems. These forms of delivery present a disadvantage of that the efficiency of the electrodeposition is lowered with time.
Likewise, this form of inefficiency is observed in the electrodeposition coating in the form of increased operational cost. Furthermore, the operation of Electrodeposition devices create natural degradation of the sacrificial element referred to as the anode. This is the internal conductive part of the device. This component wears down at a rate dependent on, but not limited to current density, pH, chlorides, etc.
The ion-exchange membrane and housing have a higher life span than the electrode by as much as 3 times. The disadvantage of placing the internal flow mechanism within the anode relates to additional cost from routine replacement of the anode and all the additional components.
Attention is called to the following U.S. Letters Patents and Publications: No. 4,676,882 issued Jun. 30, 1987 to Okazaki; No. 5,049,253 issued Sep. 17, 1991 to Izuo; and Lee, C. H., ANION-EXCHANGE MEMBRANES AND HOLLOW FIBERS PREPARATIONS, CHARACTERIZATIONS, AND APPLICATIONS, 1993; Monsanto Corporate Research Dept.
In contradistinction to each of these known systems, the teachings of the present invention embrace and finally address the clear need for a better membrane based technology having an enhanced efficacy over conventional disclosures. It is respectfully submitted that each of the discussed references merely defines the state of the art, or highlights the problems addressed and ameliorated according to the teachings of the present invention. Accordingly, further discussions of these references has been omitted at this time due to the fact that each of the same is readily distinguishable from the instant teachings to one having a modicum of skill in the art.